A problem in the field of skin grafting is the difficulty of keeping the entire area of the skin to be grafted in uniform contact with the host tissue beneath it. If even a small portion of the skin being grafted does not make proper contact with the underlying tissue, that portion can die within 48 hours. The loss area must then cover itself over by ingrowth from surrounding graft tissue that has taken. The possibilities of unnecessary scarring, and infection increase, and the entire grafting process is lengthened. While uniform skin to host contact is recognized as necessary, it has not been achieved with 100% consistency in areas involving skin motion (even though splinted) or in areas of irregular contour (such as on fingers, nose, and ears).
The most common and almost universal present-day technique of promoting uniform skin graft contact consists of tying a stent, made of left-over pieces of gauze found on the nurse's Mayo stand, over the area being grafted. As these are not designed for the purpose and ill serve it, surgeons wet the stent before cutting it to the shape of the grafted area. Others try wadded cotton wet with water or mineral oil. For a convex area, some surgeons use very stiff, large-mesh gauze. The make-shift stent is then tied over by sutures along the margin of the graft. This is a time-consuming procedure, and results in a spider web of dozens of ties along the ends of the dressing. It usually requires two persons to make the ties.
These present-day make-shift stents have ragged ends with threads and lint hanging over the ends. It is difficult to apply even pressure in small areas. The sutures usually loosen after a few days, lessening the needed pressure on the graft. Of course, excess pressure will prevent proper circulation of the graft tissue from the host and will result in slow grafting or tissue necrosis. This is typically the case in raised areas, e.g. the dorsum of the nose, where uneven, excess pressure causes sloughing. Likewise, in many instances an edge of a graft is lost because the make-shift stent did not apply even pressure at the margin.
Between the second and fifth post-operative day, some surgeons disrupt a portion of the stent to view the viability of the graft tissue or the accumulation of pus. Since the stent is opaque and only one edge is viewed, surgeons presently conclude by inference that if the one corner is good, the whole graft has survived. This often proves a false inference due to the nature of the gauze stents and tying procedures.
Another serious problem is adherence of graft tissue to the stents. Numerous materials, such as saline-soaked or mineral oil-soaked gauze, "Xeroform" brand gauze, Owin's gauze, Bacitracin or Neomycin-impregnated 4.times.4's and "Adaptic" brand sheets, have been placed over the graft to attempt to prevent adherence and tearing-off of the graft at the time of stent removal. No one present method is perfectly free of this adherence problem, and a great deal of time and soaking of stents is employed to aid their removal.
In the past, pneumatic splints or wound dressings have been provided. For example, U.S. Pat. No. 3,171,410 discloses an oval shaped (in cross-section) inflatable bladder having a gauze pad on the side facing the wound. Pressure-sensitive tape passes over the other side of the bladder and extends therebeyond to secure the bladder to the recipient (injury) site. The bladder is filled with air or gas at a high pressure, sufficient to control bleeding. Because of the oval cross section, the wound-facing side of the gas-inflated bladder is convex. This means that the bladder edges will not contact the skin surface, unless excessive pressure is placed on the assembly. Such gas-inflated structures are prone to gradual leaking of gas at the valve. To my knowledge, surgeons have not used this assembly for grafting, and it does not appear well suited to solving the grafting problems described above.
Lehmann and Hay developed an air-inflated polyvinyl plastic sheath for the arm and leg as a pressure dressing for skin grafting; Lehmann, A. L. and Hay, L. J., "A Controlled Pressure Plastic Dressing for Skin Grafting, Burns, and Thrombophlebitis," Surgery, March 1954, Vol 15, No. 3, pp 401-404. Similarly, Smith, in a short note entitled "Pressure Bags for Skin Grafting" Sug. Gynec & Obst., Vol 43, p 99 (1926) describes relatively thick, opaque, rubber, air-inflated bags of various shapes and sizes to furnish pressure dressings for Wolfe grafts. These bags are placed over a sterile vessel (probably a gauze or cotton stent) covering the graft, fixed lightly with either a gauze or lint bandage supported by adhesive tape, and inflated to a pressure of 33 mm Hg. On the 4th day the bag is deflated and the dressing opened to care for blebs or small pustules in the graft. Care must be taken not to disturb the graft in any way. The entire dressing is replaced. One design is for a nose bag, which includes an upper and lower tube for passing hot or cold water therethrough, thereby heating or cooling the graft. Schwager, R. G., and Imber, G. in "Inflatable Splint To Immobilize Extremities After Skin Grafting," Plastic and Reconstructive Surgery J., Vol 57, No. 4, p 523 April, 1976 describe the use of inflatable spints applied over traditional gauze dressing. The skin grafts are sutured in position, or held in place by a single layer of gauze stuck to the surrounding skin by collodion. An elastic bandage and the air-inflatable spint are then applied over the gauze stent. The splint extends along the entire extremity, well beyond the graft area. The dressing is changed after 48 hours. If the splint remains in place for a much longer period, which at times is necessary, excessive moisture and even purulence may accumulate. To my knowledge neither the vinyl inflatable sheaths of Lehmann or Schwager et al, nor the inflatable rubber bags of Smith are in current use by plastic surgeons for skin grafting.
Accordingly there is a need for improved methods and apparatus for applying controllable pressure uniformly over the entire graft area, even where irregular in shape or elevation, which permits easy inspection of the graft while healing is in process, and reduces the adherence problem.